The invention herein is directed to a self-sealing subcutaneous injection site. The injection site provides a resealable puncture housing for surgical implantation.
Implantable injection sites are used in patient treatment techniques wherein it is desirable or necessary to administer or withdraw a fluid to a site within a patient. Subcutaneous injection sites can be used in combination with skin expanders or inflatable mammary prostheses. The use of a subcutaneous injection site with such skin expanders and prostheses provides a means for introducing additional inflationary fluid to either the skin expander or mammary prosthesis which can be interconnected to the subcutaneous injection site. The use of a subcutaneous injection site for such medical devices provides an ambulatory condition to the patient as the patient can continue about their normal function and call upon the physician only at the time additional fluid needs to be administered or withdrawn. The use of a subcutaneous injection site in association with a skin expansion chamber is described in U.S. Pat. No. 4,217,889 to Radovan.
The subcutaneous injection site can also be used for the administration of medication to a patient. For example, in many therapeutic procedures there is a need to implant a drug delivery device. Such an implantable drug delivery device provides a bolus or therapeutic dose of the drug contained therein to a particular location within the patient's body. In order to replenish the drug in the implanted device, a self-sealing subcutaneous injection site can be provided in fluid communication with the drug delivery device. In some instances, a self-sealing subcutaneous injection site can itself be the drug delivery device. The self-sealing subcutaneous injection site provides a means for administering additional medicament into the device as the medicament can be injected using a syringe inserted subcutaneously into the injection site without the need for a subsequent surgical procedure.
Resealable puncture housing for surgical implantation are disclosed in U.S. Pat. No. 3,310,051; U.S. Pat. No. 3,831,583; and U.S. Pat. 4,190,040. U.S. Pat. No. 3,310,051 describes a silicone capsule for implantation beneath the skin into which fluid can be injected or withdrawn by hypodermic syringe. The puncturable capsule described therein works well when connected to a ventricular catheter for removing or injecting fluid into a patient's brain. However, if a high pressure is experienced by the fluid within the capsule, then the housing for such capsule can leak at the needle puncture sites, thereby causing the fluid within the capsule to flow into the surrounding tissue.
U.S. Pat. No. 3,831,583 describes a plug-shaped capsule that contains a silicone gel for resealing needle punctures of the surgically implanted capsule. The shape and dimension of the plug-like sealant chamber on such an implantable housing is not conveniently usable with the injection angle commonly used for nurses and physicians. In many instances, it is difficult to palpate and locate the particular plug-like chamber. To gain control over subcutaneous injections, the hypodermic needle is frequently placed at a widely angled position almost parallel to the skin. This gives the operator better control of the injection point and puncture depth than a position more perpendicular to the skin. Thus, the device of U.S. Pat. 3,831,583 is not ideally suitable for use.
The implantable resealable puncture housing disclosed in U.S. Pat. No. 4,190,040 was an improvement over the previous implantable resealable puncture housings. The housing in this patent utilizes a laminated structure wherein a silicone gel is sandwiched between two silicone layers. Such a device did provide for a more varied angle of penetration for a hypodermic needle being inserted into the chamber. However, the housing is not ideally structured for repeated puncturing with hypodermic needles as if a large number of punctures are desired, gel bleed from the housing can occur. In such instances, it is undesirable to have silicone gel flow into the surrounding tissue. In addition, such a device after repeated puncturing does not provide for effective sealing, particularly when the fluid in the chamber within the housing is under elevated pressures such as pressures at or near the blood pressure levels of a patient.
It would be desirable to provide a self-sealing subcutaneous injection site which can be used in situations requiring repeated and periodic puncturing while maintaining a self-sealing capability even under elevated pressures within the chamber of the injection site.